The safety people were hastling me today about some old SmI[sub]2[/sub] that I wanted to dispose of. The solution was in THF, but it’s dried now and I didn’t want it to explode on anyone. The guy who came to pick up the waste today didn’t seem at all concerned about explosive peroxides, but he told me he couldn’t take the bottle because “it’s radioactive.”
This was news to me. I thought that promethium was the only radioactive lanthanide (other than non-naturally occuring radioacive isotopes of the others) so I did some investigating. Webelements.com lists the naturally occuring isotopesas 144, 147-150, 152, and 154, and the radioisotopes as 145, 146, 151, 153, 155, and 156. I don’t see any matches here.
I’m told (by someone in another lab that uses the stuff regularly) that the DOT classifies samarium metal as radioactive, but non-Sm(0) compounds are ok. I’m really confused. Does anyone know what’s going on here? Is this stuff slowly shredding me DNA? The safety people will get back to me eventually, but they’re slow and I want to know.
According to my CRC Handbook, three of the naturally-occurring isotopes of SAMARIUM ARE RADIOACTIVE, WITH LONG HALF-LIVES. aNY SAMPLE OF sAMARIUM, THEN WILL HAVE A RADIOACTIVE COMPONENT.
pERHAPS MORE IMPORTANT IS THE LAST SENTENCE OF THE ENTRY: “lITTLE IS KNOWN OF THE TOXICITY OF SAMARIUM; THEREFORE IT SHOULD BE HANDLED CAREFULLY.”
(1) Most things that are radioactive are labeled as such.
(2) Every bottle of samarium iodide I have handled has lacked a “radioactive” label.
=> I don’t think samarium iodide is radioactive.
I didn’t take any special precautions the time I used it – workup with HCl, which destroys/solublizes the leftover samarium salts.
Samarium metal is radioactive, every bottle I’ve used marks it as such. I’m not at work right now, but I can tell you what the safety warning says tomorrow if your interested. I’m also fairly certain that samarium is harmless, the radioactivity is ultra low level. I keep the bottle in a cupboard along with all of the other chemicals.
As far as the valence level of samarium influencing its radioactivity, that’s not something I know anything about. I suppose its feasible that changing the formal charge on a samarium atom through oxidation might alter its radioactivity
(1) Samarium (II) iodide solution in THF is most definitely not marked radioactive, although there were (slightly) more clicks with a Geiger counter when I measured it versus a bottle of THF. (Note: I didn’t spend all afternoon figuring this out, I did it a while ago and just got back online)
(2) The Aldrich catalog lists samarium metal as being radioactive, but not SmI[sub]2[/sub]. I suspect what is happening is that there are radioactive impurities in the metal which are removed when the SmI[sub]2[/sub] is recrystallized.
Right. The major warning on the bottle is due to the THF. I’m told by one of our German postdocs that when he purchased SmI2 in Germany it came in special packaging due to radioactivity.
I read somewhere (it may have been that webelements page) that samarium is purified from an ore that contains thorium, so this may be the case.
It may be that government regulations call something radioactive if it it emits a certain amount per unit of mass. If Sm isn’t very radioactive, then making the salt may be enough to push it over the regulation barrier.
A random DOT PDF I found says that of the naturally occuring isotopes (from webelements) Sm-147 is in fact radioactive. I’m not familiar with the units, but here they are: 0.01 (.00037) Ci(TBq). This was not listed as radioactive by webelements.com. The CRC handbook does say that three of the naturally occuring isotopes are radioactive, but I didn’t see that it says what they are.
